This invention relates to a method of making a ballistic protective helmet and to a helmet made by the method.
Composite helmets have conventionally been made from strong fabric impregnated with a phenolic resin and cut into a hexagonal or octagonal shape called a pinwheel. Straight radial cuts are made such that the pinwheel comprises a crown from which radiates a plurality of straight-edged petals. A number of pinwheels are superposed by placing the crowns of the pinwheels on top of one another so that their petals are in a staggered relationship. The preform which results is placed in a heated mold, comprising matched steel dies, in a compression press and is subjected to heat and pressure to form the helmet.
In making the pinwheels, much fabric is cut to waste. This is a very significant disadvantage in view of the fact that the preferred fabrics comprise aramid fibers, such as “Kevlar”® sold by DuPont, and are expensive. At present there is also a world shortage, particularly of the higher grades (i.e. the strongest) aramid fibers.
The speed of the cutting procedure described above is limited by the fact that many cuts have to be made in different directions.